 /*******************************************************************************
  * Copyright (c) 2005, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/

 package org.eclipse.ui.internal.menus;

 import org.eclipse.core.commands.common.NotDefinedException;
 import org.eclipse.jface.util.PropertyChangeEvent;
 import org.eclipse.jface.util.Util;

 /**
  * <p>
  * A menu container is a menu element that can contain other elements. This
  * means that it can optionally have a class the will control the appearance of
  * elements on a dynamic basis.
  * </p>
  * <p>
  * Clients must not implement or extend.
  * </p>
  * <p>
  * <strong>PROVISIONAL</strong>. This class or interface has been added as
  * part of a work in progress. There is a guarantee neither that this API will
  * work nor that it will remain the same. Please do not use this API without
  * consulting with the Platform/UI team.
  * </p>
  * <p>
  * This class will eventually exist in <code>org.eclipse.jface.menus</code>.
  * </p>
  *
  * @since 3.2
  * @see org.eclipse.ui.internal.menus.SMenu
  * @see org.eclipse.ui.internal.menus.SGroup
  */
 public abstract class MenuContainer extends MenuElement {

     /**
      * The property for a property change event indicating that the dynamic
      * class for this menu container has changed.
      */
     public static final String PROPERTY_DYNAMIC = "DYNAMIC"; //$NON-NLS-1$

     /**
      * The class providing dynamic menu elements to this menu container. If this
      * value is <code>null</code>, then there are no dynamic elements.
      */
     protected IDynamicMenu dynamic;

     /**
      * Constructs a new instance of <code>MenuCollection</code>.
      *
      * @param id
      * The identifier of the container to create; must not be
      * <code>null</code>.
      */
     protected MenuContainer(final String id) {
         super(id);
     }

     /**
      * Returns the class generating dynamic menu elements for this menu
      * container.
      *
      * @return The class generating dynamic menu elements for this menu
      * container; never <code>null</code>.
      * @throws NotDefinedException
      * If the handle is not currently defined.
      */
     public final IDynamicMenu getDynamic() throws NotDefinedException {
         if (!isDefined()) {
             throw new NotDefinedException(
                     "Cannot get the dynamic class from an undefined menu container"); //$NON-NLS-1$
 }

         return dynamic;
     }

     protected final void setDynamic(final IDynamicMenu dynamic) {
         if (!Util.equals(this.dynamic, dynamic)) {
             PropertyChangeEvent event = null;
             if (isListenerAttached()) {
                 event = new PropertyChangeEvent(this, PROPERTY_DYNAMIC,
                         this.dynamic, dynamic);
             }
             this.dynamic = dynamic;
             firePropertyChangeEvent(event);
         }
     }
 }

